Techniques for studying hepatic metabolism in vivo.

Techniques for studying metabolic events in vivo in patients with inborn errors are reviewed. Loading or provocation tests that have been used widely are insensitive and frequently non-specific. Compounds labelled with stable isotopes can be used to study enzyme kinetics and substrate turnover, providing more detailed and specific information. Intracellular events may be studied using nuclear magnetic resonance spectroscopy. The results using these techniques to study patients with selected inborn errors are discussed, namely phenylketonuria, glycogen storage disease type I and propionic acidaemia.